SOGo is an open-source groupware server with a focus on scalability and open standards.
DAVx⁵ settings
Base URL: /dav
(e.g. https://example.com/SOGo/dav
)
If well-known URLs are configured, you can use the host name only (recommended).
Known problems
SOGo uses VLIST
vCards for contact groups, which is not specified in CardDAV and thus not supported by DAVx⁵.
There's a server problem regarding REPORT addressbook-query requests, which has been fixed with SOGo 2.3.3.